Sixty-eight percent of pregnancies among women ages 18-24 are unintended, and approximately one quarter of U.S. women in this age group have had a depressive episode in the past year. Much research at the intersection of psychology and reproductive health has focused on depression as an outcome of reproductive health experiences such as childbirth, unintended pregnancy, infertility, or contraceptive use. In contrast, this K01 Mentored Research Scientist Development Award focuses on conceptualizing depression as a precursor to unintended pregnancy among young women because using contraception requires knowledge, motivation, and a sense of agency that depressed individuals may lack. To better understand theories of fertility and to integrate demographic perspectives into my work, I propose the following career development activities: 1) obtain formal training in population and demographic research and methods, 2) develop a sound conceptualization of the role of depression in unintended pregnancy, 3) extend my statistical skill set to include longitudinal and mediational analyses, and 4) learn about and gain experience with qualitative methods. The research activities complement these training goals and are: 1) to investigate the extent to which depression influences contraceptive behaviors such as choice of contraceptive method, contraceptive use patterns, method discontinuation, and inconsistent use, 2) to use quantitative and qualitative methods to examine potential mechanisms by which depression influences contraceptive behaviors, and 3) to develop and pilot a prospective cohort study to investigate the extent to which and mechanisms by which intra-individual changes in depression influence changes in contraceptive behaviors relative to other significant explanatory factors. These endeavors will benefit from an advisory board comprised of world-renown scholars including primary mentor Nancy Adler, PhD, co-mentor Jennifer Johnson-Hanks, PhD, scientific advisor James Trussell, PhD, and scientific advisor Tina Raine-Bennett, MD. In addition, faculty consultants Chuck McCulloch, PhD, Owen Wolkowitz, MD, and Judith Barker, PhD will provide expertise in statistical analysis techniques, clinical aspects of depression, and qualitative methods, respectively. The UCSF Department of Psychiatry will provide the infrastructure to support these activities. The training and research activities proposed in this K01 will facilitate my transition to an independent investigator who takes an interdisciplinary and multi-method approach to understanding psychological aspects of reproductive health and will broaden our understanding of what leads to unintended pregnancy.